This invention relates to surface active agents and particularly amphoteric surfactants formed from amino acids.
Amphoteric surfactants have been long used and are well known for their properties of having both a cationic and anionic moiety in the same molecule. They are usually prepared by reacting a fatty amine with either acrylic acid or an acrylate ester to form beta-amino propionic acids. Primary alkyl amines contaiing 10 to 18 carbon atoms are condensed at 25.degree. to 30.degree. C with methyl acrylate to form the N-alkyl, beta-amino propionates as described in the U.S. Pat. No. 2,468,012 owned by General Mills, Inc. These products are described as being useful as detergents and foaming, wetting or emulsifying agents. U.S. Pat. No. 3,974,208 describes some of the specific amphoteric surface active agents and their manufacture which are useful as bacteriacide and foaming agents for use in shampoos. As described in the General Mills Chemicals, Inc., General Technical Bulletin 15B, amphoteric surface active agents are characterized by exhibiting changes in foaming, wetting, solubility and detergent properties with a change in pH of the solution in which the surface active agent is dissolved. Characteristically, in acidic solutions the amphoteric surface active agent is a cationic amine salt, and, in alkaline solution, an anionic carboxylate salt. If the cationic and anionic properties of the amphoteric surface active agent are in balance, the double ion is both positive and negative at the same time. This range of balance is known as the isoelectric range and the amphoteric surface active agent exhibits its minimum solubility in water, minimum foaming and minimum wetting properties. While this variance in properties with the pH of the solution is advantageous for some applications it is desirable that the variance not occur in other circumstances, particularly when a cleaning problem is involved which requires the use in situations of unknown acidity or alkalinity. Surprisingly the compounds of this invention have only slight changes in solubility over the entire pH range and exhibit superior wetting properties and a weak foam strength desirable for use in situations where foaming is undesirable.